Long before 1912 when the 300H&H came about specifically for 1000yd shooting(it was in fact designed JUST for that purpose) the 45-70 was chucking 400gr bullets 1000y at Creedmore Long Island NY.

Not quite so. Where did you get that information?

30 caliber rifles replaced the 40+ caliber international long range competition cartridges for the USA around 1900. The US Palma Team used the .30-40 Krag in 1901 and 1903. They used an experimental 30 caliber rifle in 1902 and a couple years later switched to the .30-03 and then the .30-06. Meanwhile the British Commonwealth countries had switched over to the .303 British round.

In the USA as I remember reading about the history of cartridges, the only cartridge allowed in high power rifle matches from about 1906 to 1935 was the .30-06.

The .300 H&H Mag. was introduced in 1925 as the Super 30, but was soon renamed. The H&H belted case was first used in 1912 for the .375 Belted Rimless Nitro-Express. Its belt was designed so both double rifles and bolt action magazine rifles could use the same ammo. Rimmed cases used in double rifles were not reliable in feeding from box magazines. The H&H belt prevented the top cartridge in the magazine getting its headspacing part (the rim) behind the same case part on the round below it. Those cartridges had shallow sloping shoulders so a standard rimless case could not be used; the case would be driven too far into the chamber by firing pin impact and head separation was a problem. That belt had nor does not now have anything to do with such cases being "stronger" for magnum loads.

.300 H&H's were never used in competition until 1935 when 30 caliber magnums were allowed for 1000 yard matches. Ben Comfort used a Griffin & Howe custom rifle on an Enfield 1917 action chambered for the .300 H&H to win the 1000-yard Wimbledon Cup Match at the USA Nationals in 1935. Here's a link to the details.

Never happen with the same peak pressure levels and barrel dimensions for both.

Note the .300 Weatherby magnum is a blown out version of the venerable .300 H&H; it burns more powder for the same peak pressure level and therefore pushes bullets out faster.

An awful lot of variables I agree, barrel length (dimensions) being one. I picked up my Barnes #3 manual, and reviewed the 30 magnums listed, and picked just the 200 grain bullet as that's what I would use and looked only at top velocity. 308 Norma 26" barrel 2941 fps, 300 H&H 24" barrel 2933 fps, 300WSM 24" barrel 2863 fps, 300 Winchester 24" barrel 2908 fps, 300 Weatherby 24" barrel 2934 fps, 300 Dakota 24" barrel 3018, 300 RUM 26" barrel 3134 fps (only 1 load cracked 3000 fps), 30-378 Weatherby 26" barrel 3137 fps. I can't recall which old manual (Speer I think) the 300 H&H gave the highest velocities of the magnums. It was also the only one with a 26" tube. In these standard barrel length rifles The H&H comes within 1fps of the Weatherby cut the RUM and 30-378 to 24" and watch that margin narrow. Lot's of factors in play, and I picked the facts to shape the argument my way, but 1 fps behind the Weatherby, and actually beats the Winchester by 24 fps. A little close for impossible and never happen.

I believe that Bart B's comment of "impossible" is technically accurate. You can't argue with the physics of the case capacity differences between the H&H, 300 Weatherby and 300 RUM of + 10%. I am always suspect of reloading manual data, and would not buy arguments built on this information, particularly with the 200gr.+ bullets. Choice of seating depth can make a big difference in the results. Having said that, I have thought about building a LR rig using the 300 H&H for use with 200+ grain bullets. The design does allow you to seat the long bullets out further without having the proportional impact on powder volume. Because of the long case, and the long neck of the 300 H&H you could make up a lot of the velocity difference between these cartridges using a lot less powder giving less recoil, longer barrel life, and great accuracy. It could very well be the most efficient cartridge of the lot using high BC bullets, but this would have to be proven out. I have considered trying this since I have a Pre 64 Model 70 in a magnum action 300H&H but could not bring myself to to do it because of it's excellent condition.

An awful lot of variables I agree, barrel length (dimensions) being one........ A little close for impossible and never happen.

While your data parallels many others research into cartridge load data comparing similar ones velocities, without pressure data for each one measured the same way and at the same level, it's not credible.

Another variable that's virtually always present with folks testing loads for muzzle velocity is the person holding the rifle. The same rifle and ammunition combination shot by different people holding the rifle against their shoulder as it rests atop something on a bench will produce different velocities. Sometimes differing as much as 50 to 100 fps. Which is why SAAMI uses Universal Receivers in floor mounted machine rests that present the same resistance to recoil with precision test barrels rifled and chambered to cartridge specifications. To say nothing of the differences in case neck tension on the bullet, bullet jump to the rifling, bore and groove diameters, primer, and firing pin impact will cause.

It's my opinion that the best place on the internet to make cartridge comparisons is SAAMI's web site:

That document also lists the details of the standard velocity and pressure test barrels for comparison. It's interesting that the specs for the .300 Weatherby Magnum test barrel bore diameter is larger than both the .300 H&H and Win. Mag.

For example, it lists the following for comparing the .300 H&H with the .300 Win. Mag. at 54,000 CUP:

Has visions....... I have thought about building a LR rig using the 300 H&H for use with 200+ grain bullets.

That's exactly what long range competitors thought and did after the .300's big win at the Nationals. The .300 H&H was "the" round to use in 1000 yard matches as it pushed the same bullet out about 150 to 200 fps faster than the .30-06 did with the same peak pressure. And Sierra's 200 grain SBT hunting bullet and later its FMJBT match bullet were the favorites. Winchester Model 70's were offered in a 28" bull barrel target version chambered for that .300. Winchester made 20 or so custom receivers without the magazine cutout for the US Army Rifle Team; that receiver with a totally solid bottom was one of the stiffest ever made for centerfire cartridges.

That H&H case reigned at long range until Fred Huntington (RCBS founder) came up with the .30-.338 in 1958. The .308 Norma Magnum debued in 1960 is virtually identical and was also a long range target favorite. Then the .300 Win. Mag. joined this top accuracy club in 1963.

Greyfox and Bart B,
I think impossible is technically accurate as well, and explainable when it's not. Use of the manual was to provide a common point of reference. Like I said I assembled the facts to my liking, the point was was about the variables coming together in such a way to give an unexpected (not unexplainable) result. I do think especially as barrel length increases, case capacity will more decisively rule. I was fortunate my Model 70 was not desirable as a collector. I would not buy a 300 Weatherby, and a box of ammo, sit next to Greyfox and his Model 70 on the line and ASSUME I was leaving his 60 year old rifle, and 100 year old cartridge at the gate. I agree more with what you guy's are saying than is probably coming across. Carl